There have been conventionally known toners containing a quaternary ammonium salt to improve development characteristics. For the charge control of conventional toners, JP-A-59-185353 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), JP-A-59-187357 and JP-A-62-227162 disclose capsule toners wherein a specific quaternary ammonium salt polymer is contained in the outer shell of the capsule, and capsule toner wherein a specific polymer having an amino group is contained in the outer shell of the capsule.
However, the above conventional capsule toners have disadvantages in that the environment dependence, particularly humidity dependence of chargeability is poor and a failure in charging is liable to be caused. Further, since the polymer is contained as a constituent component of the outer shell of the capsule, it is difficult to obtain a toner having satisfactory properties in both mechanical strength and chargeability. Hence, there is a disadvantage in that a degree of freedom of the choice of materials is narrow. JP-A-62-22716 discloses a capsule toner wherein a specific polymer having an amino group is contained in the outer shell of the toner. However, the polymer has a disadvantage in that the properties of photoreceptors are changed, although chargeability and the environment dependence of chargeability are improved.
The present invention has been accomplished with a view to eliminate the above-mentioned disadvantages.